The present invention generally relates to a method of forming a semiconductor device, and more particularly, to a method of forming a single sided conductor of a semiconductor device by implementing ion implantation and thermal oxidation processes.
The formation of semiconductor devices often requires processing on one side of a trench. For example, this may involve an isolation structure of dielectric layer or a conductive structure on one side of the trench, whereas the other side of the trench remains unchanged. However, as the feature size of the semiconductor device shrinks, the use of lithography technique to define the single sided conductor becomes difficult to control, or even fails to comply with the need of practical applications. Therefore, to form a sub-lithographic single sided conductor without using any extra lithography process is an advance development.
A conventional single sided conductor is generally formed by filling the trench with a conductive layer and patterning the conductive layer to form an opening on its side, that will be filled with dielectric layer in subsequent processes to achieve single sided isolation. Generally, a deposition process of dielectric is utilized to fill the opening. However, as the feature size of device shrinks, the aspect ratio of the opening is increased so that the filling ability of the deposition process is reduced resulting in voids in the deposited dielectric layer. Therefore, the effective dielectric constant of the deposited dielectric layer is significantly reduced, which accordingly influences the reliability of the device and the production yield.
Therefore, it is desired to provide a method of forming a single sided conductor without using extra lithography processes.
One aspect of the present invention is to provide a method of forming a single sided conductor, which can be a sub-lithographic feature without implementing extra lithography processes.
Another aspect of the present invention is to provide a method of forming a single sided conductor by implementing ion implantation process to enhance thermal oxidation so as to eliminate voids induced by deposition processes of filling the high aspect ratio opening.
In one embodiment, the present invention provides a method of forming a single sided conductor including providing a substrate. The substrate has an opening, which exposes a sidewall and an opening base surface. A single sided silicon layer is formed adjacent to the sidewall in the opening to expose a portion of the opening base surface. Then, the single sided silicon layer is implanted with fluorine-containing ions and thermally oxidized to form a thermal oxide layer in the opening.
Moreover, the step of forming the single sided silicon layer includes forming a silicon layer in the opening; removing a portion of the silicon layer to form a recess; forming a dielectric layer in the recess; forming a conformal polysilicon layer on the dielectric layer; ion implanting the conformal polysilicon layer to form an implanted polysilicon layer and reserve an unimplanted polysilicon layer; removing the unimplanted polysilicon layer, the dielectric layer and the silicon layer thereunder; and removing the remaining dielectric layer so as to form the single sided silicon layer. Furthermore, the step of implanting fluorine-containing ions includes implanting fluorine ions (F) or boron fluoride ions (BF2+) with a doping concentration of about 1xc3x971013xcx9c1xc3x971016 ions/cm2 at an implantation angle of about 10 to 30xc2x0 and an energy of about 5 to 20 KeV.
A further aspect of the present invention is to provide a method of forming a semiconductor device having a single sided conductor, such as a trench capacitor, which integrates ion implantation and thermal oxidation processes with the current process flow instead of deposition processes.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
FIGS. 1 to 6 illustrate cross-sectional views of forming a single sided conductor in one embodiment of the present invention.